Field of the Invention
This invention relates to sewage treatment systems, and more particularly, to a sub-surface sewage effluent disposal system which is especially designed for homes and small businesses. The system includes a primary treatment plant or tank, typically having a minimum holding capacity of 300 gallons. The primary treatment plant is designed to receive raw sewage from the home or business, treat the sewage and facilitate gravity flow of effluent from the primary treatment plant to a holding tank having an additional treatment apparatus, the effluent discharge from the holding tank being controlled by a timer and a float-operated submersible pump. The pump is connected to an electric control box located in the home or business and is controlled by the float and timer apparatus, such that the float allows the pump motor to come on when the effluent in the holding tank has reached a preselected high level, typically about 21 inches, and the pump motor cuts off when the effluent level is lowered to a preselected low level, typically about 14 inches. The total volume of treated effluent pumped from the holding tank is normally determined by the timer and not "on-demand" by the float, thus allowing controlled pumping periods determined by setting the timer at the electric control box located in the home or business. Alternatively, the timer can be bypassed to facilitate "on demand" pumping solely by operation of the float. The holding tank is also fitted with a high-water warning system which includes a warning float that is set such that there will typically be a minimum of 500 gallons of reserve capacity in the holding tank when the alarm is activated at a preselected level, usually about 30 inches of effluent, in the holding tank. When the warning float is activated, an 80 decibel audible alarm sounds in the control box located in the home or office to facilitate immediate attention due to the high effluent condition in the holding tank. The reserve capacity in the holding tank allows servicing of the pump and pump control system before overflow conditions are reached. The effluent may be further treated in the holding tank through a treatment riser located on top of the holding tank and enclosing a grate or sparger having slots or holes, upon which chlorine or other treatment tablets can be placed, to selectively treat the effluent flowing into the holding tank from the primary treatment tank. The slots or holes in the grate or sparger also serve to minimize splash and turbulence in the holding tank as the effluent enters. The effluent is pumped from the holding tank pursuant to the float and timer as described above, through a filter unit which includes a pair of filters mounted in parallel. The filters are typically 3/4 inch or 1 inch spin filters having a 150 mesh screen and are designed to constantly backwash, typically at a rate of 2 gallons per minute. The effluent leaves the filters through a check valve and enters a discharge header or manifold, where it flows through drip lines of sufficient length to dispose of a predetermined quantity of effluent, buried in the ground. The drip lines, which in concert are called a "drip field", are constructed using suitable pressure-induced, water-emitting drip hose having drip emitters typically spaced every two feet and the drip lines themselves are spaced a minimum of two feet apart and are about 2000 feet in total length from the discharge manifold to the return manifold. A vacuum breaker is commonly installed at the highest point in the drip field in conventional fashion and where the drip field fall is equal to or greater than about 4:1, pressure regulators are usually installed in the drip lines to effect a more uniform flow of effluent through the drip field. When flushing of the drip field is required, a field flush valve in the filter unit is opened and effluent flows continuously through the drip field under reduced pressure by means of the return manifold and passes through the filter unit flush return line to the primary tank treatment inlet.
It will be appreciated by those skilled in the art that a primary feature of this invention is provided wherein the two spin filters are constantly backwashed and the contaminants in the filter screens are thus washed down the filter walls and out of the bottom of the filter, through the filter backwash line and valve. The filter backwash valve is typically installed in the backwash line by means of a piece of one-half inch flexible PVC and a union and may be adjusted to control the volume of backwash effluent returned to the primary treatment tank.
One of the problems inherent in the operation of sewage treatment systems is that of producing an effluent of sufficient quality which is suitable for distribution in the ground for disposal. One way of accomplishing this result is to filter the effluent that comes from the treatment plant before it is disposed of, either in the ground or otherwise. However, many conventional filter systems are subject to plugging and high maintenance requirements make the filters extremely expensive to use.
Accordingly, it is an object of this invention to provide a simple and reliable sewage effluent disposal system which includes a specially-designed pump and casing for pumping effluent from a holding tank by operation of a unique timer and float apparatus, through a specially designed, constantly backwashed filter unit, to facilitate disposal of effluent which is well within acceptable state specifications for waste water disposal.
Another object of this invention is to provide a new and improved holding tank, submersible pump, float and timing apparatus and an effluent filter system which is used in combination with a primary sub-surface sewage treatment plant, tank or system, for treating effluent from the primary treatment tank or plant, pumping the effluent so treated through the constantly backwashed filter system according to a preselected time sequence and disposing of effluent having suitable specifications for meeting waste water disposal guidelines set up by a governing authority.
Still another object of this invention is to provide a primary treatment plant, a holding tank effluent treatment system and a float-operated submersible pump, timing and filter apparatus for a waste water disposal system, which primary treatment plant, holding tank effluent treatment system, float-operated pump, timing and filter apparatus elements are operated by an electric circuit to facilitate controlling the effluent level in the holding tank that receives effluent from the treatment plant, effecting further effluent treatment in the holding tank and allowing controlled pumping of the treated effluent through a specially designed dual spin filter unit by operation of the timer. The filter unit typically contains a pair of spin-type, automatically backwashed filters for filtering the effluent and distributing the effluent through a check valve to a conventional drip field, where the effluent is allowed to seep into the underlying soil.